PREPARATION OF A WELL-ORDERED ALUMINUM-OXIDE LAYER ON NIAL(001)

The formation of a well ordered aluminum oxide layer on NiAl(001) has been studied by means of high resolution electron energy loss spectroscopy (EELS), low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). A thin aluminum oxide film is produced by annealing the oxygen saturated surface to 1200 K. The distinct (2x1) LEED pattern produced by the film shows that it is well ordered and commensurate with the substrate. The EEL spectrum exhibits four loss peaks at 420 cm(-1), 603 cm(-1), 718 cm(-1) and 896 cm(-1). The lattice structure of the theta modification of Al2O3 matches both the LEED pattern and the EEL spectrum. The EEL spectrum can be reproduced by calculations based on the dielectric theory. From this the thickness of the oxide film is estimated to be about 10 Angstrom. A structure model for the theta-Al2O3/NiAl(001) system is given.